The goal of this proposal is to identify, isolate and characterize cell surface antigens common to murine teratocarcinomas and viral transformed mouse cells. Teratocarcinomas are known to express a number of fetal cell surface antigens and will be used as the source of "embryonic antigens" to be detected on the surfaces of viral transformed cells. Tumor transplantation rejection assays, antibody mediated cytotoxic or binding assays and cellular mediated immunity will be employed to detect antigens common to teratomas and SV40, polyoma or adenovirus type 12 transformed cell lines. Identical or cross-reacting antigens will be tested for in syngeneic (the 129 inbred strain) mouse cell lines or tumor tissues and teratomas. At least one antigen of this type has already been demonstrated (see Progress Report). These cell surface antigens will be isolated and characterized using immunoprecipitation and gel electrophoresis for this analysis. Immunoselection against these cell surface antigens will be carried out to determine if such cell surface antigens are coordinately controlled along with the transformed cell phenotype. Both cytotoxic antibodies and immune T-cells will be employed to select against viral transformed cells containing these cell surface antigens. Cell lines resistant to this immunoselection will be characterized for their transformed cell phenotype.